#!/bin/bash
#
# Activate/deactivate script for crontabs
#
# Author:	Johan De Meersman <vegivamp@tuxera.be>
# Description:	A script to failover cronjob activity, for those days when you
#               really need that extra bit of certainty.
# Syntax:       Crontab <user> <activecronfile|-r > <inactivecronfile|-r> (start|stop|restart|status)
# Config:	Not really :-) See man(8) crontab for cronfile syntax.
# Support:	Your brain, Google, Your local guru, me, Linux-HA mailing list, http://linux-ha.org/contact/ - in that order
# License:	GPL
# Revision:     1.0 - 20050421 - Initial version, should do most tricks you want.


# Source function library.
. /etc/ha.d/shellfuncs



# This is to stabilize crontab behaviour in at least some versions of Debian:
#       The  "out-of-the-box"  behaviour  for  crontab  -l is to display the 
#       three line "DO NOT EDIT THIS FILE" header that is placed at the 
#       beginning of the crontab when it is installed. The problem is that it 
#       makes the sequence
#
#       crontab -l | crontab -
#
#       non-idempotent -- you keep adding copies of the header. This causes pain
#       to scripts that use sed to edit a crontab.  Therefore,  the default  
#       behaviour of the -l option has been changed to not output such header. 
#       You may obtain the original behaviour by setting the environment 
#       variable CRONTAB_NOHEADER to 'N', which will cause the crontab -l 
#       command to emit the extraneous header.

CRONTAB_NOHEADER=Y  # We don't want no stinkin' headers



# Parameter grabbing

WHO_ME=$(basename $0)
CRON_USER=$1
CRON_ACTIVE_FILE=$2
CRON_INACTIVE_FILE=$3
COMMAND=$4



# Main functions

service_start () {
    ha_log "info: $WHO_ME: activating service"
    if [ "$CRON_ACTIVE_FILE" == "-r" -a "$(crontab -u $CRON_USER -l 2>/dev/null)" == "" ]; then
        # If you try to delete a crontab which has already been deleted, cron
        # returns with an error status. Hence this special case where we don't
        # even try.
        ha_log "info: $WHO_ME: activated"
    else
        if crontab -u $CRON_USER $CRON_ACTIVE_FILE 2>/dev/null ; then
            ha_log "info: $WHO_ME: activated"
        else
            ha_log "ERROR: $WHO_ME: Service did not activate correctly!"
            exit 1
        fi
    fi
}

service_stop () {
    ha_log "info: $WHO_ME: deactivating service"
    if [ "$CRON_INACTIVE_FILE" == "-r" -a "$(crontab -u $CRON_USER -l 2>/dev/null)" == "" ]; then
        # If you try to delete a crontab which has already been deleted, cron
        # returns with an error status. Hence this special case where we don't
        # even try.
        ha_log "info: $WHO_ME: deactivated"
    else
        if crontab -u $CRON_USER $CRON_INACTIVE_FILE 2>/dev/null; then
            ha_log "info: $WHO_ME: deactivated"
        else
            ha_log "ERROR: $WHO_ME: Service did not deactivate correctly!"
            exit 1
        fi
    fi
}

service_status () {
    # For simplicity's sake, we assume that if the running crontab matches one
    # of the config files, the service is in that state - regardless of what
    # you last asked it to do.
    RUNNING_CRON=$(crontab -u $CRON_USER -l 2>/dev/null)
    
    if [ "$CRON_ACTIVE_FILE" == "-r" ]; then
        EXPECTED_ACTIVE_CRON=""
    else
        EXPECTED_ACTIVE_CRON=$(cat $CRON_ACTIVE_FILE)
    fi 
    if [ "$CRON_INACTIVE_FILE" == "-r" ]; then
        EXPECTED_INACTIVE_CRON=""
    else
        EXPECTED_INACTIVE_CRON=$(cat $CRON_INACTIVE_FILE)
    fi
    
    case "$RUNNING_CRON" in
        "$EXPECTED_ACTIVE_CRON")
            ha_log "info: $WHO_ME: Service is active"
            ;;
        "$EXPECTED_INACTIVE_CRON")
            ha_log "info: $WHO_ME: Service is inactive"
            ;;
        *)
            ha_log "WARNING! $WHO_ME: Running configuration does not match either configuration file! Dumping into /tmp"
            DUMP_DATE=$(hadate)
            echo $RUNNING_CRON > /tmp/heartbeat.$WHO_ME.unexpected.running
            echo $EXPECTED_ACTIVE_CRON > /tmp/heartbeat.$WHO_ME.expected.active
            echo $EXPECTED_INACTIVE_CRON > /tmp/heartbeat.$WHO_ME.expected.inactive
            exit 1
    esac
}

script_usage () {
    ha_log "Usage: $WHO_ME <user> <activecronfile|-r> <inactivecronfile|-r> (start|stop|restart|status)"
}



# Grab the command(s) we need

find_command () {
    if ! which $1 >/dev/null 2>&1; then
        ha_log "ERROR: $WHO_ME: Can't find command '$1'"
        exit 1
    fi
}

# The first one's here to make sure we have what we need to find the other
# commands. No touchy-touchy. Strong bad touchy-touchy!
find_command which
find_command crontab
find_command getent



# Verify some parameters

if [ "$CRON_ACTIVE_FILE" != "-r" -a ! -r "$CRON_ACTIVE_FILE" ]; then
    ha_log "ERROR: can not read datafile $CRON_ACTIVE_FILE"
    script_usage
    exit 1
fi

if [ "$CRON_INACTIVE_FILE" != "-r" -a ! -r "$CRON_INACTIVE_FILE" ]; then
    ha_log "ERROR: can not read datafile $CRON_INACTIVE_FILE"
    script_usage
    exit 1
fi

if ! getent passwd $CRON_USER > /dev/null; then
    ha_log "ERROR: user $CRON_USER does not exist"
    script_usage
    exit 1
fi

    

# Showtime !

case "$COMMAND" in
  start)
	service_start
	;;
  stop)
	service_stop
	;;
  restart)
	service_stop
	service_start
	;;
  status)
  	service_status
	;;
  *)
	script_usage
	exit 1
esac

exit 0